The Pirate Bay is plundering your CPU for cryptocash, again

Popular file sharing site The Pirate Bay seems to have returned to its old tricks again by mining cryptocurrency in visitors’ browsers without telling them. Last month, a user called okremix posted a complaint in Suprbay, which is the Pirate Bay’s official forum.

I wanted to upload my torrents to TPB and because of the current upload error (file not found) I leaved the tab open and noticed that my CPU is getting really hot.I remember that TPB was testing background mining in the past so checked the source on upload page and there it was.

He posted a segment of JavaScript designed to mine for cryptocurrency.

Browser-based cryptominers use code embedded in a web page to force your miner into solving the complex mathematical problems that earn cryptocurrency. Instead of doing it for you, though, they do it for someone else.

Occasionally, publishers will give you the option to mine for cryptocurrency if you don’t want to read their ads. More often, crooks hack someone’s website to embed the code without their knowledge.

Sometimes, as was the case with the Pirate Bay first time around at least, the site owner embeds the code themselves but doesn’t tell visitors. When the person visiting the website doesn’t know about the mining and doesn’t give their permission, that can be classified as cryptojacking.

The Pirate Bay has done this before, using well-known miner Coinhive. This time, though, they seem to have opted for the relatively new cryptojacking service called Crypto-Loot (probably because it charges 12% commission on Monero mining, compared to Coin-Hive’s 30% commission).

Both Coinhive and Crypto-Loot focus on mining Monero, which has become the cryptocurrency of choice for cryptojackers for two reasons. First, it is CPU-friendly, meaning that miners can use a computer’s CPU in a browser without having to rely on expensive GPU hardware. Second, Monero is designed to be even more anonymous than Bitcoin, obfuscating sending and receiving addresses by default.

The mining script that okremix posted can no longer be found on the Crypto-Loot site. This is because it recently updated the code designed to connect publishers’ web sites to its own scripts and changing those scripts to avoid ad blockers. Now, it generates slightly new code.

Users responded to the news by questioning the Pirate Bay’s ethics and suggesting that they upload their files elsewhere. Forum admin Sid was less than impressed. He retorted:

Yeah, yeah, whatever. The time it takes to download a torrent is completely and utterly irrelevant.All you require from TPB is a magnet link. Open the site. Find a torrent. Click the magnet link. Close the site. End of miner.If you are ever on TPB for more than 5 minutes or so you’re doing it wrong.And if you’re ever on TPB without an ad blocker you’re doing it doubly wrong.

Quite why Sid, an admin on the official Pirate Bay forum, would trash advertising, one of the group’ big revenue sources, is beyond us. Still, it’s worth looking at how much browser-based cryptomining might earn the organisation.

Only the Pirate Bay’s crew knows its real traffic numbers, but SimilarWeb suggests that it had nearly 200 million users in the last month with an average duration of just over 5 minutes. Plugging that into Crypto-Loot’s profit calculator shows earnings of $511 per day at the current difficulty.

Mind you, that follows a considerable slide in Monero value, which has tracked the broader cryptocurrency market’s downturn in recent months. Had the Pirate Bay been cryptojacking visitors at the height of Monero’s pricing in January, it could have netted well over $1500 each day.

Although stories have been surfacing this week about The Pirate Bay’s use of cryptominers, okremix’s post dates back to 8 June. We checked The Pirate Bay’s main .org site using an unprotected browser in a virtual machine yesterday, and found no cryptomining scripts. We also visited it with a browser using a cryptomining blocker that found nothing.

Does that mean that the Pirate Bay’s electron-hogging practices are done? Don’t bet on it. Yesterday the site introduced a new disclaimer at the bottom:

By entering TPB you agree to XMR being mined using your CPU. If you don’t agree please leave now or install an adBlocker.

When checking for miners and calculating potential profits, let’s also remember the slew of proxy Pirate Bay sites, designed to help users circumvent ISPs that block its main site in their countries. Visitors in these countries can use these sites to reach its lists of magnet links, which it maintains via a cunningly-distributed back-end architecture.

The Pirate Bay maintains a list of these sites, and allows anyone to set up a proxy and submit it for approval. It exercises pretty loose controls, with the only caveats being that people shouldn’t submit generic web proxies or put too many ads on their sites. That makes it pretty easy for an independent proxy creator to mine some cryptocurrency in visitors’ browsers on the side.

We found coin miners on some, but not all, of these proxy sites. One site we visited was using a Coinhive miner, and also added another script which, in spite of the ‘install an adBlocker’ claim at the bottom of the Pirate Bay page, is designed to thwart ad blockers.

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